Method of forming a line in a gallery



May 7, 1968 P. Q. cURzlo METHOD OF FORMING A LINE IN A GALLERY Filed Oct. 30, 1964 M* @@Wfs 75 4 4 United States Patent O l 3 381 479 METHOD or roRMIG A LINE rN A GALLERY Pericle Quadri@ Curzio, Milan, Italy, assigner to Silver S.p.A. and Quadrio Curzio S.p.A., both of Milan, Italy, both companies of Italy Filed Uct. 30, 1964, Ser. No. 407,827 Claims priority, application Italy, Mar. 6, 1964, 44,777, Patent 716,578 4 Claims. (Cl. 61-45) The building of galleries or tunnels in diflicult, degraded, fractured, thrusting soils and the like, which require a load-bearing covering, involves problems in practice which were attempted to be solved in various ways. The main problem in this field is constituted by the necessity of blocking the soil as soon as possible.

It is known that as a consequence of excavation, a new ground settling tends to form; this is equivalent to the consumption of the capacity of work that had accumulated in the compressed ground and to which has been given the possibility of developing after destruction of the prexisting equilibrium.

In other words, the isolated and disgregated core that forms around the hollow increases more and more, until, after consumption of the working capacity, the formation of the core is complete. This disgregated body and especially the portion over the gallery exerts pressures upon the walls of' the excavation.

Hence the larger the volume of this core, the greater the thrusts exerted by the ground.

The building of a carrying (load-bearing) covering (coating, lining) which must necessarily have a certain thickness, requires a certain time: a brick or stone masonry lining is very slow to be made, while a concrete lining can be cast in a shorter time, to that time must be added the time needed for the preparation of the caissons and that for the cement to set.

In consideration of these inconveniences, often metallic lniugs are used, which are constituted by structural shapes or other elements which are put alongside against the wall of excavation to constitute a support thereof. Sometimes these linings are completed by injections or groutings of cement material, which however does not perform in itself any load-bearing function, but merely acts as an impermeabilizer or filter.

It has also been proposed to spray a cement mortar for rapid setting against the walls of the excavation, as soon as the latter, or a part of it, is finished, in the attempt at blocking the superficial movement of the ground during the period in which the load-bearing lining is installed;

the provisional lining so obtained is not suicient when the thrusts of the ground are conside'able. Gn the other hand, by spraying a mortar against the wall of the excavation it is not possible to build rapidly a lining of a thickness beyond certain limits, namely larger than one decimetre or litle more, because the mortar applied tends to detach itself owing to its own weight as the thickness of its layer is growing, and because a large thickness of mortar would be effected by considerable shrinking which would prejudice the final strength of the lining.

lt is an object of the present invention to obtain a definitive lining adapted to sustain the thrust of the ground immediately after making the excavation with great rapidity. For this purpose the lining after having been formed by successive arches or rings developing over the entire extension of the cross-section of the excavation to be lined so that each of those rings or arches can behave like a load-bearing frame without any discontinuity over its whole development and over its entire thickness.

Consequently the excavation can progress `for the entire` cross-section of the gallery or tunnel and for com- 3,381,479 Patented May 7, 'i968 paratively short forwarding portions, namely of the order of magnitude of one metre or even less, and at any rate not more than 3 metres. As soon as a portion of excavation is finished, its lining should be made.

This lining should be made of concrete, in consideration of the requirement it must meet; it must namely be made with a mixture of a cement binder and of a usual portion of inert stony materials, of different granule sizes but comprising at any rate granules of sizes exceeding those conventional of a sand, in practice exceeding 8 mm.

Said lining should be cast according to the invention very rapidly without employing any caissons; therefore, it is projected against the wall under strong pressure, for instance by means of compressed air.

A concrete so composed however would hardly be sustained against the wall of the excavation if the thickness of the lining exceeds certain limits, for instance 15 cm. to attain thicknesses of 30 to 50 cm. as may sometimes be required. To obviate this diiiiculty, according to the invention, near to the surface of the excavation, there is placed a reticular metal structure having a thickness of at least l5 centimetres, which with its meshes contributes to retain in place the concrete until the latter begins setting, which is promoed by an accelerating agent of any known kind introduced into the mix; said structure remains then embedded in the concrete constituting its reinforcement capable of absorbing even tension and shear stresses.

In accordance with the method according to the invention, an excavation is effected over the entire cross-section of the gallery all at once, in successive incremental lengths of less than 3 meters. An assembled reticular structure of arch shape and truss form is installed in each incremental length of the gallery after its formation, the recticular structure having a thickness greater than l5 centimeters and a surface extent corresponding to that of the walls and ceiling of the gallery and supported on the oor thereof. A mass of settable compound is injected onto the walls and ceiling of the gallery after the installation of each reticular structure such that the mass completely encases the structure and together therewith forms a reinforced lining for the excavation, the reticular construction of the structure serving to retain the settable compound on the walls and ceiling of the gallery until the compound hardens. Longitudinal reinforcing elements are installed in the gallery to which the reticular structures are successively connected.

To make the invention more fully understood, an example of a practical embodiment is hereinafter described, without limitation, making reference to the accompanying drawing in which:

FIGURE l is a diagrammatical longitudinal section of a portion of gallery in the course of building;

FIGURE 2 is a cross-section taken along the line II--II of FIGURE l;

FIGURE 3 is an enlarged View of a reticular structure used in the construction of the lining. g

FIGURE l represents the forward portion of a gallery 1 excavated in the ground, with the lining already made up to a short distance, for instance of l metre, from the front of attack indicated by 2, yassuming the excavation to have been made for this latter not yet lined portion after completion of the lining indicated in the ligure.

As soon as that portion of the excavation has been finished, there is placed in the proximity of the rocky lateral wall 3, a recticular structure constituted by four steel rods 4 whose sections are placed at the vertices of a trapezoid, and -by further steel rods 5 arranged trelliswise between the aforesaid four rods and connected at their vertices to the latter by means of welding or other means of connections; this reticle structure has the shape of a reticular arch of truss form the feet of which arch are completed by further shaped rods indicated by After putting into place this metal structure convenlently prepared before-hand and after having preferably tied it up with other rods 7 directed in the longitudinal direction of the gallery or with a metal net, there is projected against the wall 3 a mix of cement with water, sand and pebble gravel of a grain size for instance up to mm., by compressed air.

To the aforesaid mix there is conveniently added a convenient quantity of a substance adapted to accelerate the setting of the cement, for instance material of the kind of those known in the trade by the name Sika.

This mix is effectively retained, even prior to its setting, by the aforesaid reticular structure and can so constitute a lining layer 8 of suliicient thickness, for instance of to 40 cm. which hardening rapidly by effect of the aforesaid accelerator, cornes to form a new portion of load-bearing definitive lining in a very short time, before any appreciable rock burst of the vault of the excavation can take place.

In the example illustrated, the longitudinal section of the lining appears to have an undulated course, as being composed of successive small vaults; however it could also appear with substantially uniform thickness.

The pavement of the gallery can be contemporaneously completed in the shape of a casting 9 adapted to constitute a still between the piers of the arch, or there might be formed a reversed arch with or without a metal reinforcement, possibly by the same technique as above described.

On having performed all of the aforesaid operations, one proceeds with the excavation of la further section 10 of gallery repeating said operations in an identical manner.

Of course the particulars of performance as examplied hereinabove may be Widely varied; so for instance the reticular structure may assume varied sizes and shapes, other longitudinal reinforcements or armatures may be provided at the extrados and/or at the intrados or elsewhere, and the dimensions above mentioned are to be adapted to the conditions of the ground, in every specific case.

In any way, by the method of the invention it has been found to be possible to realize lining thickness much smaller as compared with the other methods used heretofore, which involves a considerable economy in the excavation, which results to be of smaller overall volume, as well as in the amount of materials needed. These results appear to be attributable to the great rapidity with which one succeeds in completing the definitive load-bearing lining, i.e., within a few hours from the finishing of each section of excavation, which prevents an undesirable alteration of the structure of the ground before the lining comes to replace the material removed by the excavation, in its load-bearing function. It should finally be noted that this rapidity constitutes also a further element of great economical advantage of the method according to the invention.

I claim:

1. A method of forming a gallery comprising excavating the gallery in successive incremental lengths of less than 3 meters, each excavation being effected over the entire cross-section of the gallery all at once, installing an assembled reticular structure of arch `shape and truss lform in each incremental length of the gallery after its formation, the reticular structure having a thickness greater than 15 centimeters and a surface extent corresponding to that of the walls and ceiling of the gallery and supported on the floor thereo, and injecting a mass of settable compound onto the walls and ceiling of the gallery after the installation of each reticular structure such that the mass completely encases the structure and together therewith forms a reinforced lining for the excavation, the reticular construction of said structure serving to retain the settable compound on the walls and ceiling of the gallery until the compound hardens, and installing longitudinal reinforcing elements in the gallery to which the reticular structures are successively connected.

2. A method as claimed in claim l wherein the settable compound is concrete having particles larger in size than 8 mm.

3. A method as claimed in claim 1 wherein said reticular structure is formed by a plurality of curved rods following the course of the vault of the gallery and connected with one another transversely by rods.

4. A method as claimed in claim 1 comprising installing a bottom casing on the floor of the gallery between the feet of the lining of the gallery for each incremental length.

References Cited UNTED STATES PATENTS 317,338 5/1885 Goodridge 61-45 1,474,808 11/1923 Zucco 61-45 1,876,205 9/1932 Crom 61-45 X 3,224,203 12/ 1965 Brannfors et al. 61-45 FOREIGN PATENTS 216,3 03 9/1956 Australia. 1,353,578 1/1964 France. 1,355,456 2/1964 France.

633,475 7/ 1936 Germany.

511,080 8/1939 Great Britain.

946,460 1/ 1964 Great Britain.

OTHER REFERENCES Cement Gun Co. bulletin 2200, pub. 1942, Allentown, Pa., pp. 54 and 55.

JACOB SHAPIRO, Primary Examiner. 

1. A METHOD OF FORMING A GALLERY COMPRISING EXCAVATING THE GALLERY IN SUCCESSIVE INCREMENTAL LENGTHS OF LESS THAN 3 METERS, EACH EXCAVATION BEING EFFECTED OVER THE ENTIRE CROSS-SECTION OF THE GALLERY ALL AT ONCE, INSTALLING AN ASSEMBLED RETICULAR STRUCTURE OF ARCH SHAPE AND TRUSS FORM IN EACH INCREMENTAL LENGTH OF THE GALLERY AFTER ITS FORMATION, THE RETICULAR STRUCTURE HAVING A THICKNESS GREATER THAN 15 CENTIMETERS AND A SURFACE EXTENT CORRESPONDING TO THAT OF THE WALLS OF CEILING OF THE GALLERY AND SUPPORTED ON THE FLOOR THERETO, AND INJECTING A MASS OF SETTABLE COMPOUND ONTO THE WALLS AND CEILING OF THE GALLERY AFTER THE INSTALLATION OF EACH RETICULAR STRUCTURE SUCH THAT THE MASS COMPLETELY ENCASES THE STRUCTURE AND TOGETHER THEREWITH FORMS A REINFORCED LINING FOR THE EXCAVATION, THE RETICULAR CONSTRUCTION OF 